This invention relates to an apparatus for processing photosensitive material, particularly silver halide photosensitive material.
In general, silver halide photosensitive material (simply referred to as photosensitive material) after exposure is subjected to a series of wet processing steps including development, desilvering, washing, and stabilization. The development step uses a developer, the desilvering uses bleaching, bleach-fixing and fixing solutions, the washing uses city water or deionized water, and the stabilization uses a stabilizing solution. These solutions are generally adjusted to a temperature of 30.degree. C. to 40.degree. C. Photosensitive material is successively dipped in the solutions for the respective processing purposes. Such a series of processing steps are most often carried out by means of an automatic processor by successively transferring the photosensitive material through processing tanks filled with the respective solutions.
The recent general demands for environmental protection and resource saving are also imposed to this type of processing. It is thus desired to save processing solutions, particularly wash water. A saving of wash water can be accomplished by increasing washing efficiency. It is known that an increased washing efficiency can be achieved by providing a plurality of washing tanks filled with wash water. One approach for achieving an increased washing efficiency with a less amount of water is a multi-stage counterflow washing mode which generally employs 2 to 9 stages. Since a plurality of wash tanks are arranged in a side-by-side relationship, the counterflow processing system is increased in size, requiring a substantial space for installation. The prior art apparatus were insufficient in saving the amount of wash water loaded and replenished.
In copending application Ser. No. 340,820 filed Apr. 20, 1989, or Japanese Patent Application No. 27034/1989 for "Method and Apparatus for Processing Photosensitive Material," the inventors proposed an apparatus for wet processing a photosensitive material, comprising a processing tank for defining an interior chamber, means for partitioning the tank chamber into a plurality of serially arranged compartments, the compartments being connected through narrow channels and filled with processing solution, and means for successively passing the photosensitive material through the compartments. This apparatus is reduced in size and successful in reducing the amount of wash water used because of increased washing efficiency. More particularly, since the compartments are connected for fluid communication through narrow channels, the degree of contamination of wash water varies among the compartments in the flow direction of wash water. Since the photosensitive material is transferred in a direction opposite to the flow direction of wash water, the material is washed with gradually cleaner wash water, leading to an increased washing efficiency.
If such operation is to be interrupted for a certain period of time, particularly in the case of water washing, it is desired to drain more or less contaminated wash water from the tank, keep the tank empty during the quiescent period, and fill the tank with fresh water again at the start of next operation. However, this drainage operation is cumbersome. Particularly when the quiescent period is not so long, the complete drainage of the wash water seems to be against the general purpose of saving wash water. If wash water is left in the apparatus, the wash waters in the respective compartments intermix during the quiescent period so that the wash waters are contaminated to an approximately equal level. Then it is difficult to accomplish efficient washing immediately after the restart of operation. A similar problem occurs with other processing solutions used in development, bleaching, bleach-fixation, and fixation.
Another problem arises with water washing through a continuous processing path comprising compartments connected through narrow channels. As in the prior art apparatus, when photosensitive material is transferred from the preceding stage tank (e.g., bleach-fixing or fixing tank) to the wash tank, the processing solution of the preceding stage tank adheres to the emulsion surface of the photosensitive material to form a thin solution layer thereon so that a double layer is created at the interface. This solution layer is obstructive to wash away chemicals present on or in the emulsion layer. Insufficient washing away of chemicals would eventually cause discoloration, fading, stain formation in prints during storage, and sticking between stacked prints. Also film properties are insufficient.
The above-mentioned problem caused by a thin solution layer adhering to the photosensitive material commonly occurs in any processing tanks into which the preceding solution is carried by the photosensitive material, resulting in insufficient photographic properties.
The developing tank which is the first tank in the process is free of the problem of adherence of a thin layer of the entraining solution. Nevertheless, the processing or reaction in a first compartment creates unnecessary or exhausted products which will adhere to the photosensitive material to form a double layer with an overlying thin layer of the first compartment solution. The thin layer of first compartment solution and the double layer are entrained into a second compartment. This results in less efficient processing.
It has become practical to recycle wash water. It is known to use ion-exchange resins as disclosed in J. Appl. Phot. Eng., 6, 120 (1980) and ibid., 5, 141 (1979) and reverse osmosis units as disclosed in USSR Patent No. 701963. Further, Japanese Patent Unexamined Publication (JP-A) No. 105150/1983 discloses the reuse of wash water by passing used wash water through a reverse osmosis unit where the wash water is separated into dilute and concentrate portions, and feeding the concentrate and dilute portions back to the bleach-fixing and washing tanks, respectively. The recycle of wash water through a reverse osmosis unit can achieve a saving of wash water when applied to a conventional wash tank. Since a great volume of wash water is subjected to reverse osmosis, however, the load of the reverse osmosis unit must be large enough. Then the unit is increased in size.